Consuming REST (GET) Service from Windows Phone 8.1

I am new to Windows Phone Development. I want to make a HTTP request to REST(GET) service from my code. The result will be in Json.

I want get my result Asynchronously and while retriving I want to show Progress Ring.

Help me solving this. Thanks in Advance.

I tried following code. But getting exception

System.Exception was unhandled by user code
  HResult=-2147417842
  Message=The application called an interface that was marshalled for a different thread. (Exception from HRESULT: 0x8001010E (RPC_E_WRONG_THREAD))
  Source=Windows
  StackTrace:
       at Windows.UI.Xaml.Controls.ProgressRing.put_IsActive(Boolean value)
       at eBooks.MainPage.GetResultCallBack(IAsyncResult result)
       at MS.Internal.Modern.ClientHttpWebRequest.c__DisplayClass1e.b__1c(Object state2)
  InnerException:

public void MakeRequest(string requestUrl)
{
    try
    {
        SearchProgress.IsActive = true;
        SearchButton.IsEnabled = false;
        HttpWebRequest request = (HttpWebRequest)HttpWebRequest.Create(requestUrl) as HttpWebRequest;
        request.BeginGetResponse(GetResultCallBack, request);

    }
    catch (Exception)
    {

    }
}

private void GetResultCallBack(IAsyncResult result)
{
    HttpWebRequest request = result.AsyncState as HttpWebRequest;
    if (request!=null)
    { 
        try
        {
            WebResponse response = request.EndGetResponse(result);
            if (response!=null)
            {
                DataContractJsonSerializer jsonSerializer = new DataContractJsonSerializer(typeof(BookSearch));
                object objResponse = jsonSerializer.ReadObject(response.GetResponseStream());
                ebook = objResponse as BookSearch;
            } 
        }
        catch (Exception)
        {
            throw;
        }
        finally
        {
            SearchProgress.IsActive = false;
            SearchButton.IsEnabled = true;
            DataLoaded(ebook);
        }
    }
}

The exception describes what the problem is. You are trying to access SearchProgress control which is a ProgressRing created on a UI thread from a non-UI thread. In order to fix this, you need to make the change from the UI thread, and for that you need the use the CoreWindow dispatcher:

CoreApplication.MainView.CoreWindow.Dispatcher.RunAsync(CoreDispatcherPriority.Normal,
    () =>
    {
        Debug.WriteLine("I'm on UI thread");
        SearchProgress.IsActive = false;
        SearchButton.IsEnabled = true;
    }
);